DESCRIPTION (from the applicant's Abstract): Purpose and Program Proposal: the purpose of this continuation proposal is to provide training in bone and cartilage research to pre-doctoral trainees in Bioengineering and to postdoctoral, post-residency trainees in Orthopaedic Surgery in order to prepare both types of trainees for academic careers. In addition, it is proposed to provide a meaningful research experience to medical student trainees as a means of attracting young, eager minds to an academic career early in their training before residency training begins. Research areas include the biology of bone growth, repair, and maintenance including origin of osteoprogenitor cells, physiological response of isolated bone cells to mechanical strain, mechanism of action or mechanical and electrical perturbation of bone and cartilage cells, characterization of transmembrane molecules (integrins) and their role as mechanical receptors; bone cell growth into porous implants; mechanisms of bioactivity produced by calcium phosphate ceramics; and the biocompatibility of particulate debris and its inflammatory response.